Apparatus for preparing paper pulp or any other product of a similar nature, from bales of cellulose or raw materials for recovery, such as waste paper

ABSTRACT

This invention provides a shredder for cellulose material in which a tank is rotatable about an inclined axis at a first speed and a shredder rotor in the tank is rotatable at a second speed greater than the first.

United States Patent Lamort [151 3,682,398 14 1 Aug. 8, 1972 [54] APPARATUS FOR PREPARING PAPER PULP OR ANY OTHER PRODUCT OF A SIMILAR NATURE, FROM BALES OF CELLULOSE OR RAW MATERIALS FOR RECOVERY, SUCH AS WASTE PAPER [72] Inventor: Pierre Louis Lamort, 47, rue de Bac 51,, Vitry-Le-Francois, France 221 Filed:" Sept. 9,1969

21 Appl.No.: 856,343

[30] Foreign Application Priority Data Aug. 25, 1969 France ..6928999 [5 2] US. Cl. ..241/46.17, 241/46.04, 241/74, 259/85 [51] Int. Cl. ..B02c 19/12, D21b 1/12 [58] Field of Search ..24l/279, 188 R, 46, 46.04, 24l/46.06, 46.11, 46.17; 259/74, 85, 42, 33, 16, 3; 162/261 [56] References Cited UNITED STATES PATENTS 2,575,380 11/1951 Borton ..241/228 X 3,115,821 12/1963 I-Iubner ....259/85 X 3,329,350 7/1967 Wisgerhof ..241/ 188 R X FOREIGN PATENTS OR APPLICATIONS 958,250 2/1957 Germany ..259/42 Primary Examiner-Andrew R. Juhasz Assistant Examiner-Michael Koezo, .Ir. Attorney-Michael S. Striker ABSTRACT This I invention provides a shredder for cellulose material in which a tank is rotatable about an inclined axis at a first speed and a shredder rotor in the tank is rotatable at a second speed greater than the first.

11 Claims, 7 Drawing Figures APPARATUS FOR PREPARING PAPER PULP OR ANY OTHER PRODUCT OF A SIMILAR NATURE, FROM BALES OF CELLULOSE OR RAW MATERIALS FOR RECOVERY, SUCH AS WASTE PAPER The present invention relates to an apparatus for preparing paper pulp or any other product of a similar nature, from bales of cellulose or raw materials for recovery, such as waste paper.

To prepare paper pulp from raw cellulose materials, the first operation consists in disintegrating the materials in the presence of water, so as to produce a substantially homogenous aqueous suspension.

At present, to perform this first operation use is made as a rule of a so-called pulper apparatus, formed by a fixed tank at the end of which a rotor, as a rule in the form of a turbine, rotates. The operation of putting the cellulose material into suspension consists in placing a certain quantity of the material in the tank, which has previously been filled with water, whereafter the rotor is rotated and vigorously churns up the water to disintegrate the cellulose material and disperses it in the liquid.

Clearly, the operation cannot be performed in this way if the aqueous suspension is fluid enough to be able to flow i.e. the concentration of dry material in the water must not be too high. In contrast, the concentration of the cellulose material in relation to the water can hardly exceed 7-8 percent, and this has the following disadvantages:

In modern paper manufacturing processes, the refining operation which follows the production of the aqueous suspension is sometimes performed with concentrations exceeding 10 percent, and may even go up to 20-25 percent. In the present day conventional pulper method, a further operation, namely thickening, must be introduced between disintegration and refining, such thickening clearly introducing a considerable complication.

When the material is cellulose material for recovery, such as waste paper it becomes progressively more difficult to disintegrate the material in the cold state, since such paper is nowadays being progressively more strongly glued or sized with various plastics materials.

To facilitate disintegration, treatment must be performed hot, but the low working density of the present day pulpers is clearly a great disadvantage in this matter, since, for instance, with a working density of 5 percent, 20 times more water than dry material must be heated, and this necessarily causes a considerable loss of calories.

The specific power is higher in proportion to the lower concentration of the mixture, due to the large amount of water to be churned up.

Another aspect of the problem of treating cellulose materials must be considered when the materials are formed by dirty waste paper, since such paper is progressively containing more and more foreign bodies I forming impurities for paper, such as inter alia all the various plastics materials which the paper may contain. Clearly, during treatment all these impurities must be eliminated; a fairly large number of processes exist for this purpose and apparatuses for performing them.

suspension flows away and which stop the passage of the impurities which cannot leave the pulper tank and accumulate therein.

Clearly, such accumulation is a disadvantage and to avoid accumulation various impurity-extracting accessories can be added to the pulper. As a rule such accessories are fairly efficient as regards heavy or thread-like impurities such as, for instance, string, but it is always substantially impossible to do anything about light impurities of any form, inter alia the majority of the plastics material which become accumulated in the pulper tank and which after a certain time require that manufacture must be interrupted for emptying and cleaning.

It is an object of the present invention to obviate these disadvantages and to allow cellulose or like materials of very high concentration (30 percent and above) to be treated and, if necessary, the impurities withheld by the discharge grids to be continuously eliminated.

The invention provides an apparatus for disintegrating cellulose raw materials and highly concentrated waste paper and cardboard for the preparation of paper pulp, the apparatus being characterized in that it is formed by a tank which is adapted to receive the raw material and is slowly rotated so as to make the raw material turn over and fall back upon itself, the axis of rotation of the tank being inclined, the tank being combined with a rotor formed with projecting edges which is disposed inside the tank and rapidly rotated to disintegrate the material.

As a development of the general idea of the invention:

The axis of rotation of the tank and the axis of rotation of the rotor coincide with one another, the rotor being disposed adjacent the inner end of the tank.

The lower portion of the tank is formed with perforations of suitable shape and size, such portion of the tank enclosed by a collector for collecting the disintegrated material.

The rotor is mounted with provision for axial displacement by a known thrust drive, the rotor being received in a corresponding opening in the end of the tank, the opening and the rotor so co-operatin g that, in dependence on the axial position of the rotor, a circular slot of varying width appears for the evacuation of the disintegrated material, the end of the tank being enclosed by a collector to this end.

The lower perforate portion of the tank is formed by a frusto-conical portion followed'by a cylindrical portion and another frusto-conical portion having an aperture in its minor base, the whole being enclosed by a collector, the rotor being formed by a cylindrical portion with projecting edges received with a small clearance in the cylindrical portion of the tank, and by a frusto-conical portion disposed in the actual tank, whose frusto-conical portion is swept by fins unitary with the rotor, the collector comprising an outlet for the disintegrated material which has passed through the perforate portions of the tank, and an outlet for the For instance, present day pulpers more particularly often have discharge grids through which the cellulose retained impurities at the end of the tank.

. The perforations in the frusto-conical portion of the tank which are swept by the fins of the rotor are formed by slots open in the direction of the minor base of the frustoconical portion, such slots being inclined in relation to the generatrices of the frusto-conical portion and in relation to the fins, so that the impurities trapped between the slots and the fins are driven by the latter in the direction of the openings of the slot.

The portion of the end of the tank enclosing the rotor comprises a chamfer whose pointed edge is disposed on the inside of the tank, and the rotor comprises a substantially disc-shaped portion whose face turned towards the inside of the tank is formed with projecting edges, the periphery of the rotor rotating with a small clearance in relation to the pointed edge of the chamfer, the disc surface turned towards the. inside of the tank determining, by its position in relation to the pointed edge of the chamfer, an opening of varying size for the disintegrated material, so that a portion of thickness D of the material thrown by the turbine passes through the opening thus formed, the opening being equivalent to a screening of the material through slots of width D.

The width of the slots between the projecting edges of the rotor corresponds to the required fineness of the material, the upper ridge of the edges extending beyond the pointed edge of the chamfer in the direction of the inside of the tank, so that those impurities or particles which cannot pass through the slots are rejected in the direction of the inside of the tank, so that a double screening is produced by means of two perpendicular slots, one of the slots being formed by the gap between the projecting edges of the rotor and the other by the opening of width D between the rotor and the end of the tank.

The height of the projecting edge is greater at the periphery of the rotor than towards the center.

The arrangements according to the invention obviate the necessity of the whole mixture being churned up by the rapid disintegrating rotor, since such churning up can be produced by a slow movement of the tank assembly.

In practice such movement is a slow rotation which rolls the material round the inside of the tank, constantly bringing each portion of the mixture into contact with the disintegrating rotor, which can thus per form its work in the whole of the material to be treated, without having to churn it up. Clearly, an apparatus of the kind specified is adapted to treat materials of any required concentration, since the rotation of the tank can churn up even a completely dry material.

The invention will be more readilyunderstood from the following description of exemplary embodiments thereof, with reference to the accompanying drawings, wherein:

.FIG. 1 is a sectional elevation of a first embodiment of an apparatus according to the invention;

FIG. 2 is a sectional elevation of a second embodiment of the invention;

FIG. 3 is a detail of FIG. 2;

FIG. 4 is a sectional elevation of a third embodiment of the invention;

FIG. 5 is a partly sectioned view of the apparatus il- ,lustrated in FIG. 4, shown in a different working posi- Referring to the drawings, the apparatus is formed by a tank 1 of revolution, generally formed by two frustums and terminating at its lower end in a journal 6 supported by a bearing 7, the tank comprising at its upper end a wide circular opening 1c enabling the material to be treated to be introduced. Adjacent the opening 10 the tank 1 can, in the case of large-scale apparatuses, comprise a trackway 3 moving on rollers 4.

A shaft 9 retained by a bearing 8 extends through the hollow journal 6 and bears a disintegrating rotor 2 generally of frusto-conical shape. The tank 1 and the disintegrating rotor are rotated around their respective axes which as a rule coincide with one another but may in some cases differ from one another. As a rule, the speed of rotation of the tank 1 will be slow and that of the rotor 2 fast, the directions of rotation being identical or opposite. Thus, the shaft 9 carrying the rotor 2 may be driven directly by a motor M whereas the hollow journal 6 to which the tank 1 is connected may be driven from a motor M over a spaced reducing gearing 20, 21 as schematically illustrated in FIG. 1.

The tank 1 has an emptying gate 5 which can be manually or mechanically opened; in the latter case a device (not shown) can readily be provided which enables the door to be opened while the tank is rotating.

The inclinationa of the axis of rotation of the tank 1 to the horizontal depends on the materials treated and can even be adjusted by conventional mechanical devices.

The periphery of the rotor 2 is formed with radially and axially projecting fins 2a whose number and shape can vary in dependence on the various materials for treatment. In all embodiments the outer edges of the fins extend at the end of the rotor 2 adjacent the bottom end of the tank further away from the axis of rotation than at the other end of the rotor.

The inner surface of the tank 1 can be formed with projecting edges, if necessary.

Operation is as follows: with the tank 1 and the rotor 2 rotating, the dry material to be treated plus the required amount of water is introduced through the aperture 1c.

The mixture rolls around in the tank 1, and due to the shape of the tank 1 and its inclinationa such movement constantly brings each portion of the mixture on to the rotor 2 which, due to its speed and its edges 2a, progressively disintegrates the material. When disintegration is complete, the door 5 is opened and the crushed mixture flows away, whereafter the operation starts again.

The apparatus according to the invention allows hot treatment; to this end it is enough to use hot water and, if necessary, to heat-insulate the tank 1.

If treatment is to be performed at a temperature above C, it is enough to provide an autoclave cover which closes the opening 10 and to supply the heat, for instance, steam, through the hollow journal 6.

The apparatus shown in FIG. 1 performs intermittent treatment; for treatment to be continuous, with the continuous separation and evacuation of the impurities, it is enough to provide an apparatus such as that shown in FIG. 2.

The lower portion la of the tank 1 is continued by a cylinder 1d and then by a frustum If. The walls of the cylinder 1d and of the frustum 1f are formed by plates formed with openings of suitable shape, as a rule holes or slots, so as to produce a screen.

The portion la of the conical base of the tank 1 is also formed by perforated plates forming a screen.

The rotor 2 has a shape such that'its fins 2a and the fins 2b follow the profile of the screens 14 la, and sweep the surface thereof at a small distance during their rotation. The surface of the portion 1 f is not swept by the fins 2a. The rotor 2 is retained by a shaft supported at its two ends by bearings 8, 8a.

A hopper 10 supporting the bearing 8a can be provided to facilitate charging via the opening 1c.

Operation is as follows:

The tank 1 is slowly rotated and the rotor 2 is quickly rotated. The material to be treated and a certain amount of water is charged via the hopper 10, the material then being rolled around and constantly turned over in the tank 1. As a result of the shape and inclination of the tank, the material is constantly brought into contact with the rotor 2 which, due to its speed, disintegrates the material. The adequately disintegrated material passes through the perforations of the screen 1a, while the portion of the element inadequately divided and the impurities which cannot pass through the screen la are thrown back inside the tank 1 where they continue to undergo the disintegrating treatment. However, elements which have been unable to pass through the screen 1a come into the zone of the screen 1d where they undergo further disintegration which enables them to pass through the screen 1d. The impurities which could not be divided are retained by the screen 1d and make their way to the zone of screen If accompanied by a residue of material which has not yet had the time to pass through the screen 1d. The screen If then acts like a sizing drum and finally releases the impurities from the satisfactory material which they still contain. Lastly, the fully screened impurities leave via the open end lg and drop into the collector 11b, while the disintegrated material is collected in the collector 1 l and recovered via the outlet 1 la.

The apparatus shown in FIG. 2 therefore continuously produces a disintegrated and purified cellulose pulp of high density and also continuously evacuates the impurities in the material to be treated.

The passage of the material through the screens la, id is accelerated by the centrifugal action of the rotor 2 whose edges and fins 2b pass by immediately adjacent the screens.

If necessary, the screens la, 1d and 1f can be cleaned during operation, either continuously or periodically, from outside by means of either a scraper, jets of air, steam or water, in any known manner.

In a special embodiment of the screen 1a (FIG. 3), the perforations are formed by slots 17 having a width corresponding to the sizes of the particles of the disintegrated material. The slots 17 are open at the inner end 17a and form an angle 60 smaller than 90 with a circle 18. The object of the resulting grid is to obviate the following disadvantage: particles 1b of material thrown on to the grid by the fins 2b of the rotor 2 have a tendency to accumulate at the edge of the openings of the grid, due to the speed at which they impinge on the grid. If the slots are perpendicular to the direction of movement of the fins 26 of the rotor 2 they are therefore rapidly clogged up; if the slots are parallel to the direction of movement, the material accumulates at.

their ends and they progressively get clogged up. The solution to the problem was found by inclining the slots 17 by an angle 60 in relation to the fins 2b, so that the material stopped by the edge of the slot tends to slide towards its inner end 17a which is opened so that the material cannot accumulate there.

In the variant embodiment shown in FIGS. 4-7, the end 1h of the tank 1 is formed with an opening receiving a rotor 2 with a disc-shaped portion 2c with a small clearance j. The disc 20 and the development of the rotor 2, which can be of varying size, bear projecting fins 2a. The rotor can be moved axially by abutment 9a, 9b and a drive 12 articulated at a place 13. The end opening 1h has a chamfer 14 whose pointed edge is on the face of the joint 1h facing towards the inside of the tank 1.

Operation is as follows: during the working phase of the apparatus (FIG. 4), the axial position of the rotor 2 is so adjusted that the disc 20 is slightly forward, towards the inside of the tank 1 in relation to the lower surface of the end 1h. The particles of material thrown by the rotor 2 have trajectories A which are substantially continuous in the plane of the disc 20, so that in view of the small clearance j between the disc 20 and the opening, none of the particles can leave the tank 1. When the apparatus is to be emptied, without stopping its rotation, the rotor 2 is so moved in the outward direction that the disc 2c is slightly withdrawn in relation to the pointed edge of the chamfer 14 (FIG. 4). Clearly, under these conditions at least a portion of the particles thrown by the rotor will leave the tank 1 through the annular space between the chamfer l4 and the edge of the disc 2c, following the trajectory B. In contrast, if a particle of material has a thickness greater than the distance D between the surface of the disc 2c and the inner surface of the end 1h, the particle will not be able to leave the tank 1 and will follow the trajectory A.

This device therefore enables the apparatus to be unloaded while performing the screening of the particles forming the material under treatment. The device also enables the apparatus to operate continuously, due to the screening thus performed, which allows to escape only adequately processed material freed from its main impurities.

Another advantage to be noticed is that the fineness of screening thus performed can be adjusted during operation, since it depends mainly on the distance D, much more than on the clearance j, between the diameters of the disc 20 and the opening. The fact is that the trajectories B of the particles at the outlet from the rotor 2, in view of the speed thereof, are substantially rectilinear and continuous in a plane normal to the axis of rotation, so that screening consists in separating, by the pointed edge of the chamfer 14, a portion of material having a thickness equal to the distance D. The result is therefore substantially the same screening as that obtained with a grid whose apertures are slots of a width equal to the distance apart D, but the great advantage is that in the present case adjustment can be performed during operation, whereas the width of the slots of a grid cannot be so adjusted.

If the material to be treated contains a large amount of flat impurities 16 having a thickness smaller than the distance apart D and therefore able to escape with the screened material, the periphery of the disc 20 (FIGS. 6 and 7) can be formed with a succession of projections whose height H is greater than the distance apart D, and which are circumferentially spaced from each other through a distance L which is smaller than one smallest flat dimension of the thin particles 16 to be separated. If one of these particles 16 is considered, it can be seen that as a rule it comes to the rotor 2 flat, and in view of the spacing L, the particle cannot be introduced between two projections 15 and is as a result obliged to follow the trajectory A and is therefore separated from the accepted material which follows the trajectory B.

Having described my invention, I claim:

1. Apparatus for disintegrating cellulose raw material, waste paper and cardboard in the presence of water for the preparation of paper pulp, said apparatus comprising a tank adapted to receive the raw material and being rotatable about an axis inclined to the vertical; means to rotate said tank at a first speed to cause raw material in the tank to turn over and fall back upon itself; a rotor generally of frusto-conical configuration disposed inside said tank adjacent the lower end thereof, said rotor having an axis of rotation substantially coinciding with that of said tank and fins extending in axial direction of said axis of rotation and radially away from the same, the outer edges of said fins extending at the end of the rotor adjacent the bottom end of said tank further away from the axis of rotation than at the other end of said rotor; means to rotate said rotor at a second speed greater than said first speed to disintegrate the material; and means for at least partially evacuating the disintegrated material from said tank.

2. Apparatus as set forth in claim 1, wherein said means for at least partially evacuating the disintegrated material from said tank are located in a lower portion of the latter and are formed by perforations of suitable shape and size, and including collector means enclosing said portion of said tank for collecting the disintegrated material.

3. Apparatus as set forth in claim 1, wherein said means for at least partially evacuating the disintegrated material from said tank comprises a door movable between open and closed position provided in a lower portion of said tank.

4. Apparatus as set forth in claim 1, wherein said tank is formed at the lower end thereof with ,an opening, wherein said rotor is axially displaceable, and ineluding thrust means to axially displace said rotor, said rotor having an end portion received in said opening of said tank and defining therewith a circular slot of varying width dependent on the axial position of said rotor, said slot constituting said means for at least partially discharging the disintegrated material from said tank; and including collector means at said lower end of said tank for collecting the disintegrated material.

5. Apparatus as set forth in claim 2, wherein the lower perforate portion of the tank is formed by a frusto-conical portion followed by a cylindrical portion and another frusto-conical portion, having an aperture in its minor base, the whole being enclosed by a collector, the rotor being formed by a cylindrical portion with projecting fins received with a small clearance in the cylindrical portion of the tank, and by a frusto-conical portion disposed in the actual tank, whose frusto-conical portion is swept by fins unitary with the rotor, the fililii'wifillili %le l"ilgugi ui' glioli 3i?? tions of the tank, and an outlet for the retained impurities at the end of the tank.

6. Apparatus as set forth in claim 5, wherein the perforations in the frusto-conical portion of the tank which are swept by the fins of the rotor, are formed by slots open in the direction of the minor base of the frustoconical portion, such slots being inclined in relation to the generatrices of the frusto-conical portion and in relation to the fins, so that the impurities trapped between the slots and the fins are driven by the latter in the direction of the openings of the slot.

7. Apparatus as set forth in claim 4, wherein the opening in the end of the tank enclosing the rotor comprises a chamfer whose pointed edge is disposed on the inside of the tank, and the rotor comprises a substantially disc-shaped portion whose face turned towards the inside of the tank is formed with projecting edges.

8. Apparatus as set forth in claim 7, wherein the width of the slots between the projecting fins of the rotor corresponds to the required fineness of the material, the upper ridge of the fins extending beyond the pointed edge of the chamfer in the direction of the inside of the tank, so that those impurities or particles which cannot pass through the slots are rejected in the direction of the inside of the tank, so that a double screening is produced by means of two perpendicular slots, one of the slots being formed by the gap between the projecting fins of the rotor and the other by the opening of width D between the rotor and the end of the tank.

9. Apparatus as set forth in claim 8, wherein the height of the projecting fins is greater at the periphery of the rotor than towards the center.

10. Apparatus as set forth in claim 1, wherein said tank comprises two portions of frusto-conical shape integrally connected at the large-diameter ends thereof.

11. Apparatus as set forth in claim 1, wherein the inner surface of said tank and the edges of said fins define between themselves a free uninterrupted space. 

1. Apparatus for disintegrating cellulose raw material, waste paper and cardboard in the presence of water for the preparation of paper pulp, said apparatus comprising a tank adapted to receive the raw material and being rotatable about an axis inclined to the vertical; means to rotate said tank at a first speed to cause raw material in the tank to turn over and fall back upon itself; a rotor generally of frusto-conical configuration disposed inside said tank adjacent the lower end thereof, said rotor having an axis of rotation substantially coinciding with that of said tank and fins extending in axial direction of said axis of rotation and radially away from the same, the outer edges of said fins extending at the end of the rotor adjacent the bottom end of said tank further away from the axis of rotation than at the other end of said rotor; means to rotate said rotor at a second speed greater than said first speed to disintegrate the material; and means for at least partially evacuating the disintegrated material from said tank.
 2. Apparatus as set forth in claim 1, wherein said means for at least partially evacuating the disintegrated material from said tank are located in a lower portion of the latter and are formed by perforations of suitable shape and size, and including collector means enclosing said portion of said tank for collecting the disintegrated material.
 3. Apparatus as set forth in claim 1, wherein said means for at least partially evacuating the disintegrated material from said tank comprises a door movable between open and closed position provided in a lower portion of said tank.
 4. Apparatus as set forth in claim 1, wherein said tank is formed at the lower end thereof with an opening, wherein said rotor is axially displaceable, and including thrust means to axially displace said rotor, said rotor having an end portion received in said opening of said tank and defining therewith a circular slot of varying width dependent on the axial position of said rotor, said slot constituting said means for at least partially discharging the disintegrated material from said tank; and including collector means at said lower End of said tank for collecting the disintegrated material.
 5. Apparatus as set forth in claim 2, wherein the lower perforate portion of the tank is formed by a frusto-conical portion followed by a cylindrical portion and another frusto-conical portion, having an aperture in its minor base, the whole being enclosed by a collector, the rotor being formed by a cylindrical portion with projecting fins received with a small clearance in the cylindrical portion of the tank, and by a frusto-conical portion disposed in the actual tank, whose frusto-conical portion is swept by fins unitary with the rotor, the collector comprising an outlet for the disintegrated material which has passed through the perforate portions of the tank, and an outlet for the retained impurities at the end of the tank.
 6. Apparatus as set forth in claim 5, wherein the perforations in the frusto-conical portion of the tank which are swept by the fins of the rotor, are formed by slots open in the direction of the minor base of the frusto-conical portion, such slots being inclined in relation to the generatrices of the frusto-conical portion and in relation to the fins, so that the impurities trapped between the slots and the fins are driven by the latter in the direction of the openings of the slot.
 7. Apparatus as set forth in claim 4, wherein the opening in the end of the tank enclosing the rotor comprises a chamfer whose pointed edge is disposed on the inside of the tank, and the rotor comprises a substantially disc-shaped portion whose face turned towards the inside of the tank is formed with projecting edges.
 8. Apparatus as set forth in claim 7, wherein the width of the slots between the projecting fins of the rotor corresponds to the required fineness of the material, the upper ridge of the fins extending beyond the pointed edge of the chamfer in the direction of the inside of the tank, so that those impurities or particles which cannot pass through the slots are rejected in the direction of the inside of the tank, so that a double screening is produced by means of two perpendicular slots, one of the slots being formed by the gap between the projecting fins of the rotor and the other by the opening of width D between the rotor and the end of the tank.
 9. Apparatus as set forth in claim 8, wherein the height of the projecting fins is greater at the periphery of the rotor than towards the center.
 10. Apparatus as set forth in claim 1, wherein said tank comprises two portions of frusto-conical shape integrally connected at the large-diameter ends thereof.
 11. Apparatus as set forth in claim 1, wherein the inner surface of said tank and the edges of said fins define between themselves a free uninterrupted space. 